This invention relates to system performance simulators, and specifically to an analysis mechanism which allows a designer to investigate and interact with a simulator to determine, qualitatively, and quantitatively, how well a system being simulated performs during a simulation.
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A simulator which incorporates a hardware description language is described in U.S. Pat. No. 5,092,780 to Vlach, for SYSTEM PERFORMANCE SIMULATOR, granted Mar. 3, 1992. The system performance simulator described in the Vlach patent includes a library having a number of templates therein, where each template represents, mathematically and operatively, real-world, physical devices. Templates each include one or more mathematical equations which are descriptive of the behavioral characteristics of the represented physical device. Such templates are part of what has become to be known as a hardware descriptive language (HDL). Templates may be combined with a quantitative value set, also contained in the library. A template which is combined with a quantitative value set is referred to as a component model, which represents a specific real-world device.
The library further includes a system topology which describes how the individual devices are connected. A system assembler is operable to take the equations from the individual component models and form them into a set of system equations for the system which is to be simulated. A core simulator then performs the actual simulation by solving the system equations and provides an output. Other features of the system performance simulator include the ability to define an expression and to build templates using a modeling subsystem.
The system performance simulator described in the Vlach patent includes what are referred to as conservation properties, which are located within the templates and which contain the necessary mathematics to simulate conserved, physical systems. Additionally, environmental parameters are included in the templates and component models to provide a simulation which is sensitive to changing environmental conditions, such temperature, pressure, etc.
U.S. Pat. No. 4,868,770 for SIMULATION RESULTS ENHANCEMENT METHOD AND SYSTEM, granted Sep. 19, 1989 to Smith et al., further describes the system performance simulator of Vlach as including a results enhancement software which is operable to produce a simulation completion results database. A certain amount of post processing may be done on the completion results database which enables a designer to view or plot a dependent variable or a transform thereof from the modeling subsystem. This provides the Capability of interrupting the simulation upon the occurrence of a designer-defined event, such as the overloading of a physical circuit component, which is mathematically acceptable to the simulator, but which will result in the failure of the physical, real-world device.
While the aforementioned technologies are suitable for their intended purposes, it is desirable to be able to extract additional indicators of design quality from a system performance simulation wherein such indicators will provide a quantitative and qualitative measurement of sensitivity within the system, the amount of stress on the system, to be able to perform a worst case analysis on the system, to be able to simulate failure modes and the effects thereof, and to provide a centering and tolerancing analysis. All of these quantitative and qualitative measures of performance require the ability to extract an individual quantitative measure from the data set that is the result of the system performance simulation.
While such analyses have been done in the past, the techniques for accomplishing such analyses are, to say the least, cumbersome. For instance, in order to determine the sensitivity of a system, as where one component is changed and the effect of such change is to be analyzed with respect to other components, a designer must run an entire series of individual simulations wherein the device parameters for a physical device are manually and/or individually varied in the model, or in the representative code, for that device, and the results of such variations are analyzed with respect to the other system components. This is obviously a very time consuming process.
Likewise, a stress analysis may be accomplished manually by observing all operating parameters and noting those which are operating outside of their design envelopes. However, as previously noted, the simulator will simply perform a mathematical analysis. The simulator has no concept of "failure", as the mathematics will not necessarily indicate that a part is not operating, but will provide information which is used by the remainder of the system equations. The '770 patent discussed above, provides a method for stopping a simulation if the operational envelope of a particular component is exceeded, but does nothing to indicate how the rest of the physical system which is being simulated will perform as a result of the failure of a particular component thereof.
It is possible in known HDL models to simulate a specific part over a range of device parameters by manually changing the device parameters within the model during successive simulation. However, such an HDL model does not offer the capability of having a range of parameters specified therein. Therefore, the simulator will not, on its own, provide an analysis mechanism which operates within a range of parameters and which will detect and report primary and secondary component failures.